DatumNest: Tolerance Stack

About DatumNest: Tolerance Stack

DatumNest is a tolerance stack-up workbench for product engineers, machinists, quality teams and engineering students. Build a signed one-dimensional dimension chain, then see worst case, RSS, modified RSS, statistical and Monte Carlo results side by side, with Cp, Cpk, predicted yield and ppm against your spec limits.

NEW IN 2.0
- Unlimited saved stacks in millimeters or inches
- Asymmetric tolerances (e.g. 10.000 +0.000/−0.120), editable sensitivity coefficients and fixed (purchased) parts
- Method comparison: worst case, RSS, modified RSS (1.5 × RSS), distribution-aware statistical ±3σ and Monte Carlo
- Cp, Cpk, predicted yield and ppm out of spec
- Seeded, repeatable Monte Carlo with 10,000, 50,000 or 100,000 runs, histogram with spec limits and percentiles
- Tolerance allocation: resize adjustable tolerances to make the worst case fit or reach a Cpk target, saved as a new stack
- Mean centering and a "best part to tighten" ranking
- Side-by-side comparison of two saved stacks
- CSV import and export of dimension chains
- Full backup and restore of every stack (restore never deletes; a safety copy is kept)
- PDF engineering report with histogram, methods and chain
- A written method guide with formulas and a worked example computed live by the app

HOW IT WORKS
Walk the loop around the closing gap and enter each contributor with its nominal, plus and minus tolerance, direction (+ or −), sensitivity and distribution (normal ±3σ, uniform or triangular). DatumNest converts unequal tolerances to their midpoint and half-width, sums them, and shows which contributors own the variation so you know what to tighten first.

PRIVATE AND ONE-TIME
Everything runs on your device. No account, no subscription, no in-app purchases, no ads, no analytics and no network use. Your stacks stay in the app until you export them.

DatumNest is an engineering screening and communication tool. Confirm datum schemes, geometric effects, correlations, distribution assumptions, process capability, units and acceptance criteria with qualified design and quality personnel.